Protective system for electrical apparatus connected with polyphase networks



S p 1952 w. J. TURNUPSEED ETAL 2,609,425

PROTECTIVE SYSTEM FOR ELECTRICAL APPARATUS CONNECTED WITH POLYPHASENETWORKS 2 SHEETS-SHEET 1 Filed Oct. 24, 1949 Winifred J. TumupseedHarley E Tumupseed mmvrons BY WWW gm S P 2, 1952 w. .1. TURNUPSE ED ETAL,609, 5

' PROTECTIVE SYSTEM FOR ELECTRICAL APPARATUS CONNECTED WITH POLYPHASENETWORKS Filed Oct. 24. 1949 2 SHEETS-SHEET 2 Inventors Winifred J.Tumupseed Harley E. Tumupseed By W iatented Sept. 2, 1952 PROTECTIVESYSTEM FOR ELECTRICAL APPARATUS CONNECTED "WITH POLY- PHASE NETWORKSWinifredJ. Turnupseed; Porterville, and Harley I E. Turnupseed, Tulare,Calif.

Application October 24, 1949, Serial No. 123,172

3 Claims.

This invention relates to protective systems for polyphase circuitscontaining electric motors especially induction motors and otherapparatus and it has for its main object to provide a completeprotection against interruption or abnormal voltage drops in one phaseline of the system.

It is well known that ,the normal overload protection used in A. C.networks is inadequate under certain conditions in polyphase networks,especially when a large number of electric motors is connected'with' thenetwork. When, for instance, an interruption in one of the phase linesof a polyphase system occurs by the blowing of a fuse in said line fromsome other causes, the motors connected with the network continueto run,the power being supplied by the remaining phase or phases, The extraload may lead. to a burning out of the motor. A similar overloading isthe consequence of a marked or abnormal voltage drop inone phase line. sI

Customarily protection of the apparatus and motors connected with apolyphase network is obtained "by means of special overload relays whichare preferably used concurrently with a low voltage release device. Suchan arrangement gives good results in most networks, but does noteliminate completely the danger of burning out of a polyphase motor inthe event of a'phase line interruption, as such a protection isdependent on the heating or on the adjustment of the overload relaywhichis usually determined by other circumstances. It has therefore beenproposed to use in a three phase system, for instance, two

overload relays between the network and the au- 5 tomatic 1 interrupter,usually called magnetic switch, and one or two no-load or undervoltagerelays in the phase lines, sometimes arranged at the same spot andsometimes arranged between the-automatic circuit breaker and the motoror apparatus connected with the network.

These systems are relatively complex and they also entail thearrangement of further relays for controlling the flow of currentthrough the automatic circuit breaker and through relays controlling theno load feature of the no load relays.

Arrangements of these types also, in many cases, entailthe use of aseparate source of current for starting the electric motors.

Itis the object of this inventionto smpny this arrangement and to reduceit to the absolutely essential number of protective devices which arepreferably so constructed that they may directly cooperate with theoverload relays, thus reducing the equipment practically to threecombined relays in a three phase system, for invention employs onlythree additional series relays to afford full protection by guardingagainst those overloads which are caused by an interruption of voltagein any one phase line of a polyphase network.

Further and more specific objects will be apparent from the followingdetailed specification.

The invention is illustrated by Way of example in the accompanyingdrawing showing two embodiments thereof. It is however to be understoodthat the examples given have been selected in order to explain theprinciple of the invention and the best mode of applying this principle.Modificationsof the embodiments which have been illustrated aretherefore not necessarily departures from the essence of the invention.

In the drawing:

Figure l is a circuit diagram of the connections of the protectivesystem according to the invention.

Figure 2 is a diagram of the relay used according to the invention forprotection against current failure in a phase line.

Figure 3 is a diagram of the connections of the system according to theinvention using improved overload relays.

usually a single phase in a three phase network.

Such protection is especially desirable in networks supplying a verylarge number of electric motors, as is the case for instance, in an oilfield, where a defect caused by one motor may lead to damage in manyunits.

In orderto give full protection against overloads as Well as againstunder voltage, it is preferable to provide a system with protectivedevices separately responsible to overloads clue to an interruption of aphase line and to overloads due to other sources, which system useshowever merely a single circuit breaker operated by the said device.

A three phase network has been selected as an example. The systemcomprises a single automatic circuit interrupter 5 which may be part ofa more elaborate structure, such as a compensator, but which is shown inFigure 1 merely as an automatic circuit provided with an operating coil6 tripping four switch or contact arms II, l2, [3, I4, by means of asuitable armature l. Three of said'switch'or contact arms control thethree phase lines l5, I6, I! which are supplied with current from thethree phase network 8, 9, l0. Between the switch or contact arms and thenetwork the fuses l8, I9, 20 are inserted, protecting against overloadsdue to certain defects.

It may be mentioned that the fuses do not offer sufiicient overloadprotection, as every motor is subjected during the starting phase andalso during operation to high momentary overloads which do not damagethe motor. Such overloads must be tolerated, as otherwise greatinconvenience would result from the constant blowing of fuses.Thereforain addition to these fuses, overload relays 2i, 22in Figure 1,23; 24, 25 in Figure 3 have been arranged in order to permit highoverloads of a momentary character, while sustained overloadsareoperating the overload relays.

In the modification of the invention shown in Figure 1, which figureillustrates the principle of the invention, only two overload relays 2I, 22 are arranged which in this case are of the well known typeoperated by heater units, a typewhich is most frequently'used and neednot be illustrated or described. These relays have their heating coilsarranged in the phase lines I5, I! leading to the three phase motor M.The phase .lines l5, I6, I! also contain the relay coils 26, 21, 28 ofthe under load relays-each of which is provided :with an armature 29,30, 3| normally held inan open position by spring action or the like,while these armatures will close or bridge contacts 33, 34,-.35-

upon energization of the relay coils.

The fixed contacts 33, 34, 35 of these relays are arranged in series andform part of acircuit 40 which branches off from one of the phaseconductors H at a point 38 located between the network and the circuitinterrupter 5. This circuit also includes the fourth switch arm 14 ofcircuit breaker 5 and, after having passed the fixedcontacts 35, 33, 34of the three .underload relays, is.

connected with point 43 on the starter. device.

The starter device 4| includes the twopush buttons 36, 37 for startingand stopping the. electric motor. These buttons, as usual, afterhavingbeen pressed, return to their original .position shown in Figure 1. Thestarter device moreover includes two circuits'42, 44 .one including thestarter button contacts 36, theother the stop button contacts 37 whichcircuits are joined with each other and with circuit 40. at junctionpoint 43.

The circuit 42 branches off from one of the phase conductors I! eitherdirectly or by using a junction point 39 on circuit 40 connected withphase line 5?, while circuit 44 includes the coil 6 of the circuitinterrupter 5 and is connected with another phase line 16 at a point 45,arranged between the circuit interrupter contact l2 .and the network.

The construction of the. under load relays is illustrated in Figure 2..Therelay comprises a laminated frame structure Silwiththree legs. 51,52, 53. On the central leg 5!, the. coil 54 is mounted, the winding ofsaid coil being connected.

with one of the phase lines as shown in Figure 1,

On one leg 53 an armature 68 ispivotally mounted cooperates with thefixed contact 59 on contact strip 6|,which is fixedly mounted on butinsulatedfrom leg 52 of the frame structure 50. Contacts 58;.59-correspond to contacts 33, 34, 35 of Figure 1 and coil 54 correspondsto coils 28, 26, Not this figure.

Obviously, upon energization of the coil 54, con tacts 58 .and59 areclosed, while upon de-energization of the coil 54 the contacts are heldopen by. spring 56.

The fixed contact strip 6! and the movable contact strip 51 arebothprovided with terminal screwspermitting connection of the contactswith v the circuit 40.

The arrangement shown in Figure 1 isobviously. much simplified. whencompared with. known arrangements of an. automatic circuit breakercontrolled by protective relays whichis combined with a start and stopcircuit. A single. circuit 40 withtwobranches 42, 44 containsinv series,all the under load relay contacts, the-circuit breaker coil and thestart and stop buttons. This circuit therefore is the sole additiontothe. customary arrangement.

The operation of the arrangement will be readilyunderstood b-y-assumingfor instancethat. the motor is first started by pressing starterbutton36. This closes circuits 42, 44 which include coil 6 of the circuitbreaker 5. Coil 6 thereby moves its armature I from its positionof rest.shown in Figure 1 to its operative position-closing theswitch arms I I,l2, l3 and -l4, and thereby connectingthe phaseconductors l5, l6, ITwith. the network 8, 9, l0; The electric motor, which may; bev aninductionmotor, will thereupon start and run normally. Whenthe pushbutton. 36: is released the coil 6 remains. in the circuit and isenergized over circuit 40 which includes, the contacts 33, 34, 35 of theunderload relays.-

During, such normal operation current. will. flow through the heatercoils 2|, 22andthrough allthree under load relaycoils .26, 21, 28..

It will be noted. thatthevfuses l8, I9, .20 must beso selected thattheycan stand thehig-h overload, which usually is more thanthree timesthe normal amperage, occurring at-the starting of the induction motor.Such a momentary overload will notafiect theoverloadrelays which, aswellknown, are always delayed actionrelays, operating in this instance bymeans of .heatingcoils. The time delay must be such that under normalload conditions they operate before .the motor has been heatedsufficiently to be: dam agedi However, on account of the timedelayandlof. the. adjustment of these relaystheyfail topro tectsuificiently against overloads due to phase interruption. In. the eventof such. an. inter: ruption, for instance c'ausedby theblowing. of fuse[8,: the current in phase line l5 fails .-and relay 28. is de-energized,opening. contacts 351 Circuit 40- is interrupted and 00116 becomes.de-energized. The. circuit breaker. is. thereby tripped. and returnsinto the position. shown. in Figure 1in which the phase lines areopened.

Thev modification of the. invention which .is'.

illustrated in Figure 3 shows a practical example of the cooperation ofoverload relays and under load relays, making practically a-single unitout of these two relays.

The circuit arrangement is essentially the same as that shown in Figure1 except for the fact that overload relay coils 23, 24, '25 have beensubstituted for the heater coils 2 I, 22. The relays 23, 24, 25 nowcooperate with the under load relays indicated at 26, 21, 28 and thiscooperation is illustrated in detail in Figure 4.

The overload relay 66 shown in Figure 4 is of a well known type which iswidely used and it comprises a solenoid coil with a core H ,to which apiston 12 is attached. moving in an oil sump T4. The piston moving inthe oil produces the required time lag on one hand and in addition alsoenables the operator to adjust the time lag and to adjust the current atwhich the relay should operate. W

A pin 15 arranged in the top structure of the relay operates the contactspring 16 when, the

solenoid core has been attracted by the coil. The relays of this typeare usually encased in a casing 'I8 and are mounted on a suitablesupport 19 in the manner shown. With these known relays the contactspring 16 normally rests on fixed contact 11 and the contacts aretherefore closed until opened by the upward movement of the core 1!.However with the modified construction illustrated in Figure 4 thecontacts 16, H are normally open. g

According to the invention the under load relay 80 is added to thisrelay construction. The under load relay comprises substantially thesame parts which have already been described in connection with Figure2, but in this modification the strip 51 does not carry a contact butmerely carries a hinge ill to which a plunger pin 82 is attached. Theplunger pin passes through a guide 84 and rests on the contact spring 16of the overload relay. Its weight does not close contacts 16, H but anyelectromagnetic action of the relay 80 immediately closes the contacts15, H.

The coil 85 of the under load relay is connected in series with the coil10 of the overload relay. The relay 88 has therefore no specialcontacts, but operates contacts 16, I1 conjointly with the overloadrelay 66.

The operation is very similar to that already described in connectionwith Figure 1, except that in this case the contacts 16, I1 are the solecontacts which are operated, thus simplifying the cooperation betweenthe overload relay and the under load relay.

When the motor has been started by pressing button 36, both coils 28,23; 26, 24; 21, 25; corresponding to coils l0 and 85 in Figure 4, areenergized. Armature 60 of relay 80 is therefore attracted and pushes pin82 downwardly thus closing contacts 16, 11.

The current surge at the start and the normal current flowing throughcoil 10 do not operate the overload relay 66 because the oil seal holdsthe piston 12 back.

If however an overload occurs, lasting for sometime, the heavier currentdue to the overload now flows through the coil l6 and moves the pistonslowly upwardly and finally by means of pin l5 trips the contacts 15,ll. Therefore circuit 4G is interrupted and coil 6 is tie-energized asthis coil (as explained in connectionwith Figure l) is included incircuit as. The circuit breaker 5 therefore opens the switch armswhenever an overload will occur.

On account of the delayed action and also on accountof the necessaryadjustment of the current flowing throughthe coil which is adapted tooperate the relay the overload relay itself is not capable of protectingthe induction motor against single phase overloading. However, under thesystem contemplated by the invention, if an under voltage or aninterruption in one of the phase lines, say in phase line [5, shouldoccur, relay 89 will release armature 60 and plunger pin 82 will nolonger hold contacts 16 pressed against contact ll. Thereby the circuit40 is again interrupted, coil 6 is de-energized, and the switch arms ll,[2, Hal i are opened thereby and the motor is entirely cut off from thenetwork.

It will therefore be seen that the arrangement according to theinvention provides a simplified and effective protective system,safeguarding motors and other apparatus connected with a polyphasenetwork against all failures which may occur.

It is also to be understood that the details of the construction may bechanged and varied in many wayswithout affecting the essence of theinvention as the structural details of some of these relays are notessential for the system.

Having described the invention, what is claimed as new is l pln aprotective system for polyphase networks in combination, anunder-voltage relay having an open frame carrying the relay coil andhaving an armature hinged to said frame and closing the open side ofsaid frame when attracted by the relay coil, a member projecting fromsaid armature and a push rod hingedly attached to said projection, anoverload relay provided with a casing having an insulated cover, acontact making resilient member mounted on said cover, a fixed contactmounted for cooperation with the said resilient member on said cover,said resilient contact member being operatively positioned so as to bemoved towards the said fixed contact by the push rod of theunder-voltage relay, and movable means operative by said overload relayacting on said resilient contact member to move it away from the fixedcontact upon operation of said overload relay.

2. A protective system for polyphase networks with phase linescontrolled by an automatic electromagnetically operated circuit breaker,including an operating coil and a plurality of armatures, cooperatingwith fixed contacts controlling the phase lines, comprising a startercircuit, including a normally open start contact switch, a normallyclosed stop contact switch, both returning to their normal positionafter operation, and the operating coil of the circuit breaker,connected on one side with one phase line and on the other side withanother phase line, an overload relay in each of said phase lines and anunderload relay in each of said phase lines, a single contact pair ineach phase line operated by the overload relay and underload relay ofeach phase line cooperating with each other, each of said relays havingindependently operable electromagnetically controlled means acting onsaid single contact pair, the overload relay opening and the underloadrelay closing said contact pair during energization, a circuit brancharranged in parallel to the section of the starter circuit containingthe normally open start contact switch, said circuit branch including afurther armature and fixed contact of the electromagnetic circuitbreaker, and further including all the single contacts controlled by thecooperating pairs of overload and underload relays in. series, saidcontactszbeingiclosed when the; underload relays are" energized;;thuskeepingscthe starter circuit'supplied With;current after ther'operation: and i return of the start": contact' switch;- but making;operation dependent on predeter= mined vvoltage and:currentzconditionsiin all phase lines. provided with cooperating relay pairss 3. Aprotective systemion polyphase networks with phase lines controlled: byanautomaticrelec tromagnetically: operatedtcireuit: breaker, include:ing an operating coil and a pluralityofarmatures; cooperating. withfixed contacts r controlling: 1. the phaselines, comprisinga starter=circuit, including'a normally open start contactswitch, anormally closedstopcontact'switch; both returning to their normal positionafter:operation, andthe opera-ting coilof the circuitbreaker; connected on oneside with one phase line and on the other side with another phase line,an overload-relay ineach of said phase lines-and an underload relayineach of said phase lines, a single contact pair in :each phaseline-operated by the overload/relay and underload relay of each phaseline-cooperating with eachother, each of said relays beinglocatedona'difierentsideof-saidcontact pair. and each being provided with. a pushmember movingon one of the contacts offlthesinglevpairluponenergization, said push member being moved byranelectromagnetically operated. membenof. the respective relay, theoverload relay closing-and the under-load relay opening the. con-tactpair during: energization, a circuitbranch arranged .in .parallel to thesection of the starter cirlcuit containing. the normally open startcontact switch, said-circuit branch including a further armature andfixed contact of.. the electromagnetic circuit breaker, and furtherincluding all the single con.-

RiEEERENGESrOIT-ED The following references are *of record-in' the fileof this-patent? UNITED-STATES J'PATENTS Number I-T2itrze= new 9691345Giilyer sent; 6; 1910 1,063,179 Burnham Ji1ne =3, 1913- 1,-1'79 ,-63'7Kruse Apr: 18-31916 '1;-189 ,4G9' Van A'lstynem July.'4,'-19161,199344'7 Wilfiande'r a Sept. 26919 16 1;3-14;332 Jones; Augx 265 1919-l,'775;658 Seger Spt1691930 18003256 Keller ADP! 14} 1931 $060,481?Austin Nov: 10, 1936 2,43 1;886 Pavitt l Dec; 2; 1947 FOREIGN -;PATENTsNumber: Country: Date Germany o Mar;"-22, 1935 OTHER+REFERENCES 1Electrical Review-article; pages-8212823; issue of Nov.- 22; 1946;

